1. Field of the Invention
This invention relates to improvements in depth gauges and methods for using them, and, more particularly, to a depth gauge the scale of which is visible with X-rays and to a method for using same in surgical techniques.
2. DESCRIPTION OF THE PRIOR ART
Various types of depth gauges have been proposed for general use, and for surgical use in particular.
For example, in general, a depth gauge is shown by Kinney, U.S. Pat. No. 1,248,340, and includes an elongated rod onto which a scale or graduations are formed. A shoulder is carried on the rod and is movable along its axis. When the rod is inserted into a cavity or hole the depth of which is to be measured, and the shoulder brought to rest on the edges of the structure forming the hole, the depth of the hole can be readily measured or determined from the scale or graduations.
With respect to depth gauges for particular use in surgical environments, Biscow, U.S. Pat. No. 2,394,140, shows an obstetrical measuring instrument in which a scale is formed onto a finger of a flexible glove for directly measuring distances into cavities into which the fingers can be inserted.
Other surgical devices have been proposed for measuring various distances, such as surgical device described by Rubricuis, U.S. Pat. No. 3,740,779. This device is formed upon a surgical scalpel, and includes metered markings along its elongated axis for direct measurement, much like an ordinary ruler. At one end, a taper is formed for measuring circumferential diameters of an orifice, and, additionally, an arm is attached to the scalpel through a pivot pin to move out therefrom to serve as a caliper.
The instant invention, as will become apparent from the description below, has a principal use in performing orthopedic surgery of the type in which two or more sections of bone are immobilized by the insertion of a pin or wire therethrough. In this connection, the patent to Huene, U.S. Pat. No. 3,867,932, should be noted. This patent discloses a clamp assembly for immobilizing opposed segments of a fractured bone, and includes a drill which is used in conjunction with the clamp, operable to drill into the bone to a predetermined depth.
However, in the performing of most orthopedic surgical operations, especially those involving the hip bone, or other bones contained in a socket, the clamping device of Huene cannot be employed since the portion of the bone to which the clamp would otherwise be attached is inaccessible. Ordinarily, in such operations the surgeon performing the operation drills a hole into the two sections of the bone to be joined, exercising caution to insure that the drill bit does not penetrate beyond the end of the bone, for example, into the hip bone socket. The drill bit is then removed and a bone joining pin is then driven or inserted into the preformed hole. After the pin is in place, it is ordinarily cut where it protrudes adjacent the outer edge of the bone piece to be joined. This cut, however, often leaves exposed sharp edges upon the pin. After the operation is completed, these sharp edges, then deeply within the patient's body, are often a source of irritation to the patient upon movement of the limb into the bone of which the pin has been inserted.
To overcome this difficulty, it has been proposed that the bone joining pin to be inserted be precut so that its dimensions are precisely that desired to be employed in the bone joining operation. Thus, any sharp edges can be removed prior to the surgical procedure. However, since the dimensions of the pin needed are not known, due to many factors, such as the age of the patient, the location of the break in the bone, and so forth, a variety of pin lengths are required to be on hand prior to the commencement of the operation in readiness for use. This leaves the problem as to the choice of the pin of the appropriate length needed.
The difficulty in determining the precise depth of the hole which has been formed between the bones to be joined can be appreciated if one considers the inaccessability of the area, for example, of the hip joint. If X-ray techniques are employed, care must be taken that the angle which the X-rays penetrate the pin receiving hole be precisely right angles so that its depth can be precisely measured, without being foreshortened by an angular perspective which would otherwise result. (Ordinarily, X-ray equipment is available, and, in fact, may be used during the drilling process to insure that the drill bit does not cut beyond the desired region and into the joint or socket.)